300 RUM might have a very slight velocity advantage, but I still think the 7STW is better. I think the STW might have better barrel life b/c of how hot the RUM is. The RUMs have horrible throat erosion b/c of how overbored they are. The STW isn't the best on throat erosion itself, but should be better than the RUMs.
There are people who have ahot the STW over 1,500 yards. Used to be a video on YouTube, but I can't seem to find it anymore. I'm sure tou could wffectively shoot elk that far with a hot load of H1000 and some Berger 180 VLD's.